Leaking rod packing is not a problem unless it is excessive. Depending upon the particular service, excessive leakage can result in reduction of cylinder discharge pressure, release of toxic or noxious gases, and in some cases, contamination of crankcase lubricants. Excessive leakage eventually results in the need for a maintenance shutdown. In many cases, it also results in some loss in plant throughput since compressors may not be fully spared.
In many instances, rod condition is partially or totally responsible for this excessive leakage. A rod should be reconditioned before wear is so excessive that required coating thicknesses (to build it back to original dimension) exceed 20-30 mils. In many cases, coating processes are less successful when more than a 30-mil buildup is required. Peeling, spalling and fragmentation problems are commonly encountered.
Rods are most successfully reconditioned if required coating thickness can be held to less than 10 mils.
Other factors which affect the sealing ability of a packer include:
• Gas pressure,
• Gas properties (molecular weight, corrosivity, wetness),
• Supply of proper quantity and type of lubricant,
• Break-in procedure (refer to Section 700), and
• Type of packing material and packer design.